Antireflective coating

ABSTRACT

Device and method for an antireflective coating to improve image quality in an image display system. A preferred embodiment comprises a first high refractive index layer overlying a reflective surface of an integrated circuit, a first low refractive index layer overlying the first high refractive index layer, a second high refractive index layer overlying the first low refractive index layer, and a second low refractive index layer overlying the second high refractive index layer. The alternating layers of high refractive index material and low refractive index material form an optical trap, allowing light to readily pass through in one direction, but not so easily in a reverse direction. The dual alternating layer topology improves the antireflective properties of the antireflective layer and permits a wide range of adjustments for manipulating reflectivity and color point.

This application is a divisional of application Ser. No. 11/314,772,filed Dec. 21, 2005.

TECHNICAL FIELD

The present invention relates generally to a device and method useful inan image display system, and more particularly to a device and methodfor an antireflective coating to improve image quality in an imagedisplay system.

BACKGROUND

Image display systems that employ image projection techniques, such asspatial light modulators (SLMs) using arrays of digital micromirrordevices (DMDs), deformable mirrors, and liquid crystal on silicon, cansuffer from a degraded contrast ratio (a ratio of brightest white todarkest black producible) due to reflections of a light used to projectthe images from parts of the arrays not intended to reflect light. Lightcan scatter from support structures, apertures, vias, and so forth fromthe array of light modulators. The scattered light can effectivelyreduce the darkness of the darkest black, therefore reducing thecontrast ratio. For example, in an SLM using DMD technology, light canscatter from electrode structures, micromirror support structures,mirror vias, and so on.

One technique to reduce reflection is to place an antireflective coatingon metal structures in the array of light modulators. Since the metalstructures can be a significant source of unintended reflection, the useof the antireflective coating can significantly improve the contrastratio. For example, uncoated aluminum can have a reflectivity as high as92 percent while coated aluminum can have a reflectivity ofapproximately two to three percent.

One disadvantage of the prior art is that the application of theantireflective coating on the metal structures does not address theunintended reflection from other portions of the array of lightmodulators, such as the interlayer dielectrics, the substrate material,metal structures buried under dielectric layers, and so forth.

A second disadvantage of the prior art is that by not addressing thelight reflecting off the non-metallic structures, it is possible to havean undesired change in the color point by using different layerthicknesses. Changes in the thicknesses of the interlayer dielectriclayers can have an especially pronounced effect upon the color point.Changing the color point can result in an undesired colorcast to theimages being displayed.

SUMMARY OF THE INVENTION

These and other problems are generally solved or circumvented, andtechnical advantages are generally achieved, by preferred embodiments ofthe present invention which provide a device and method for anantireflective coating to improve image quality in an image displaysystem.

In accordance with a preferred embodiment of the present invention, asemiconductor device with an antireflective coating is provided. Thesemiconductor device includes a first high refractive index layeroverlying a reflective surface of an integrated circuit and a first lowrefractive index layer overlying the first high refractive index layer.The semiconductor device also includes a second high refractive indexlayer overlying the first low refractive index layer and a second lowrefractive index layer overlying the second high refractive index layer.

In accordance with another preferred embodiment of the presentinvention, a method for forming an antireflective coating on asemiconductor device is provided. The method includes forming a firsthigh refractive index layer on a reflective surface and forming a firstlow refractive index layer on the first high refractive index layer. Themethod also includes forming a second high refractive index layer on thefirst low refractive index layer and forming a second low refractiveindex layer on the second high refractive index layer.

In accordance with another preferred embodiment of the presentinvention, an integrated circuit is provided. The integrated circuitincludes a first layer overlying integrated structures of the integratedcircuit, the first layer comprising a first material with a highrefractive index and a second layer overlying the first layer, thesecond layer comprises a second material with a low refractive index.The integrated circuit also includes a third layer overlying the secondlayer, the third layer comprises a third material with a high refractiveindex and a fourth layer overlying the third layer, the fourth layercomprises a fourth material with a low refractive index.

An advantage of a preferred embodiment of the present invention is thatit also reduces unintended reflections from the non-metallic portion ofthe array of light modulators, as well as reflections from structuresthat are buried underneath the dielectric layers. The result is adisplay system with a better contrast ratio, and hence, better qualityimages.

A further advantage of a preferred embodiment of the present inventionis that the color point can be stabilized so that there is substantiallyno undesired colorcast to the images being displayed, even if themanufacturing process introduces wide variations in the thicknesses ofthe interlayer dielectric layers.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiments disclosed may be readily utilized as a basisfor modifying or designing other structures or processes for carryingout the same purposes of the present invention. It should also berealized by those skilled in the art that such equivalent constructionsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIGS. 1 a and 1 b are diagrams of an SLM system and a detailed view of across-section of a light modulator array;

FIGS. 2 a through 2 c are diagrams of an antireflective coating forstructures in an integrated circuit, according to a preferred embodimentof the present invention;

FIGS. 3 a and 3 b are diagrams of antireflective coatings, according toa preferred embodiment of the present invention;

FIGS. 4 a through 4 c are diagrams of sequences of events in thefabrication of an integrated circuit with an antireflective coating,according to a preferred embodiment of the present invention; and

FIGS. 5 a and 5 b are diagrams of reflectance vs. light wavelength for alight modulator array with and without the antireflective coating,according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to preferredembodiments in a specific context, namely an SLM system using digitalmicromirror devices (DMDs) as light modulators, wherein the SLM systemcan make use of any number of light component colors. The invention mayalso be applied, however, to other SLM systems, such as those usingdeformable mirror or liquid crystal on silicon light modulators, as wellas other applications where there is a need to reduce unintendedreflections. Examples of these applications include light modulatorsused in non-display applications, including displacement monitors,accelerometers, photolithography, and so forth, as well asmicro-electromechanical (MEM) devices used, for example, in laserpointers.

With reference now to FIG. 1 a, there is shown a diagram illustrating anSLM system 100. The SLM system 100 features a light source 105 thatprovides light to a light modulator array 110. The light modulator array110 contains a plurality of light modulators (not shown) that manipulatethe light to display an image on a display plane 115. The lightmodulators in the light modulator array 110 can make use of a widevariety of light modulator technologies, such as positional micromirror,deformable mirror, liquid crystal on silicon, and so forth. Fordiscussion purposes, the focus will be placed upon positionalmicromirrors used in a digital micromirror device (DMD). However, thisshould not be construed as being limiting to the spirit and scope of thepresent invention.

Depending upon a positional micromirror's position, light from the lightsource 105 can either reflect onto the display plane 115 or to someother portion of the SLM system 100. The light reflecting onto thedisplay plane 115 forms the image being displayed and the lightreflecting to another portion of the SLM system 100 is not visible onthe display plane 115. Therefore, the state of picture elements can bedisplayed. If a picture element (or a group of picture elements) is tobe on, then a positional micromirror(s) associated with the pictureelement will reflect light from the light source 105 onto the displayplane 115 and the portion of the display plane 115 will be lit. On theother hand, if the picture element is to be off, then the positionalmicromirror will reflect light from the light source 105 to a differentportion of the SLM system 100 and the portion of the display plane 115will be dark.

However, light from the light source 105 can reflect from structures onthe light modulator array 110 other than the light modulatorsthemselves. This unintended reflection can have a negative effect on theSLM system's contrast ratio, thereby reducing overall image quality. Forexample, it is possible for light to reflect from apertures, vias,support structures, electrode structures, micromirror supports, and soforth on and in the light modulator array 110.

With reference now to FIG. 1 b, there is shown a diagram illustrating adetailed view of a portion of the light modulator array 110, whereinpositional micromirrors are used as light modulators. The diagramillustrates a portion of the light modulator 110 with three positionalmicromirrors, such as positional micromirror 150. The diagram alsoillustrates other structures making up the light modulator array 110,such as a positional micromirror structure 160, electrode structure 165,and so forth. Additionally, there can be structures such as vias 170,metal conductors 175, and so on buried beneath or in a modulating layer180. It is possible for light from the light source 105 to travelthrough gaps, such as gap 185, present between adjacent positionalmicromirrors and strike these structures (as well as a top surface ofthe modulating layer 180) and scatter. The light from the unintendedreflections can strike the display plane 115, degrading the contrastratio of the SLM system.

As discussed previously, a prior art technique makes use of anantireflective coating applied to metal structures that are external tothe modulating layer 180. A similar term, antireflective layer, can beused interchangeably with antireflective coating without affecting thespirit of the present invention. The antireflective coating can reducethe amount of unintended reflection. However, the application of theantireflective coating on the external metal structures does not addressreflections from structures buried under the modulating layer 180 orundesirable scatter from the top surface of the modulating layer 180.Furthermore, a problem with color point variation as a function ofvarying layer thicknesses of an interlayer dielectric used to providepassivation to the modulating layer 180, which can lead to undesirablecolorcast being present in images displayed by the SLM system, is notaddressed in the use of the antireflective coating on the external metalstructures. According to a preferred embodiment of the presentinvention, it is possible to apply an antireflective coating underneaththe top surface of the modulating layer 180 so that reflections fromstructures buried under the modulating layer 180 can be reduced as wellas providing a stable color point for widely varying interlayerdielectric thicknesses.

With reference now to FIGS. 2 a through 2 c, there are shown diagramsillustrating an antireflective coating that can be applied to areflective surface to reduce reflectivity and an exemplaryantireflective coating applied on a metallic surface, according to apreferred embodiment of the present invention. The diagram shown in FIG.2 a illustrates reflective surface 205, such as a metal structure, andan antireflective layer 210 that can be applied on top of the reflectivesurface 205. Alternatively, rather than applying the antireflectivelayer 210 on individual structures, the antireflective layer 210 can beapplied on top of an entire layer. For example, if a modulating layer,such as the modulating layer 180 (FIG. 1 b), has metal layers one, two,and three (with metal layer three being a topmost metal layer), then theantireflective layer 210 can be applied on top of the modulating layerafter metal structures are formed in the metal layer three. Theantireflective layer 210 can then cover the entire modulating layer andcan reduce reflections from all structures in and beneath the modulatinglayer.

According to a preferred embodiment of the present invention, theantireflective layer 210 comprises four layers of material withdiffering refractive indices, with alternating layers of high refractiveindex material and low refractive index material. More than four layerscan be used, however, the effectiveness of the antireflective layer 210may not increase significantly with additional layers. Preferably, afirst layer 215 of the antireflective layer 210 has a high refractiveindex. For example, the first layer 215 can be formed using TiN(titanium nitride) or silicon rich nitride (SiRN). A second layer 220 ofthe antireflective layer 210 should have a low refractive index and canbe formed from a dielectric metal oxide, such as silicon dioxide (SiO₂),aluminum oxide (Al₂O₃), or silicon oxynitride (SiON). A third layer 225of the antireflective layer 210 should have a high refractive index andcan be formed using the same material as was used to form the firstlayer 215. Alternatively, a different material may be used in the thirdlayer 225. A fourth layer 230 of the antireflective layer 210 shouldhave a low refractive index and can be formed using the same material aswas used to form the second layer 220. Alternatively, a differentmaterial may be used in the fourth layer 230. Depending upon thematerial used for the fourth layer 230, a passivation layer may beapplied to provide a measure of protection for the antireflective layer210 and underlying structures. For example, if silicon dioxide is usedto form the fourth layer 230, it may not be necessary to add apassivation layer.

It should be understood to those skilled in the art of semiconductormanufacturing that the stoichiometry of these layers may not be exact.Thus in addition to the nominal compositional elements, amounts of otherelements may be present. For example, in the case of titanium nitride,commonly denoted TiN, the stoichiometric, crystalline compound is Ti₃N₄.However, a titanium nitride thin film is better represented asTi_(x)N_(y)O_(z), where x, y, and z are integer values and y>x>z. Thisis due to the deposition method for the TiN layer, which typicallyinvolves reactive sputtering of Ti metal in a nitrogen-containingplasma.

The layers in the antireflective layer 210 effectively function as alight trap to prevent light that passes through the antireflective layer210 and reflects from the reflective surface 205 from passing backthrough the antireflective layer 210. The thicknesses of the layers inthe antireflective layer 210 can be determined after considering factorssuch as: wavelength of the light being reflected, desired color point,amount of permissible reflection, and so forth.

The diagram shown in FIG. 2 b illustrates an exemplary antireflectivecoating formed from four layers of materials with differing refractiveindices, wherein the antireflective coating is formed on top of thereflective surface 205 made of aluminum. The first layer 215 of theantireflective coating can be made using TiN (with a typical refractiveindex of around 2.5), the second layer 220 of the antireflective coatingcan be made using SiO₂ (with a typical refractive index of around 1.4)or SiON (with a typical refractive index of around 1.6), the third layer225 of the antireflective coating can be made using TiN, and the fourthlayer 230 of the antireflective coating can be made using SiO₂. Althoughshown in FIG. 2 b as being made from TiN, the high refractive indexlayers, the first layer 215 and the third layer 225, can also be madefrom semiconducting metals, a metal oxide, or a metal nitride with arefractive index of at least 1.7. The thicknesses of the low refractiveindex layers (the second layer 220 and the fourth layer 230) can bereferred to as thicknesses L1 and L2 and can range from 3 nm(nanometers) to 10,000 nm, with a preferred thickness range being 10 nmto 2,500 nm. While a preferred low refractive index material is SiO₂ orSiON, a wide variety of materials with a refractive index between thatof air and TiN can be used, for example, insulating metal oxides andmetal halides with a refractive index of less than 1.7 can be used.Additionally, materials such as aluminum (Al); titanium (Ti); tantalum(Ta); tungsten (W); silicon (Si); chromium (Cr); alloys of Al, Ti, Ta,W, Si, Cr; silicon dioxide (SiO₂); silicon oxynitride (SiON); titaniumnitride (TiN), titanium aluminum nitride (TiAlN), and titanium dioxide(TiO₂), with TiN, TiAlN, and TiO2 being exemplary members of compoundsdescribable as semiconductive binary and ternary compounds, can also beused. The two high refractive index layers (the first layer 215 and thethird layer 225) can have thicknesses (referred to as thicknesses H1 andH2) chosen to minimize the intensities of undesired reflections from thecompleted structure. Layer thicknesses for H1 and H2 range from 5 nm to1000 nm, and preferably from 5 nm to 250 nm. The diagram shown in FIG. 2c illustrates thickness ranges for the layers of the antireflectivecoating.

The dual high refractive index layers (the first layer 215 and the thirdlayer 225), shown in FIG. 2 b as being made from TiN, are arranged inwhat is commonly referred to as a split layer geometry. Each of the twohigh refractive index layers has a low refractive index antireflectivecoating. For example, the first layer 215 has the second layer 220 asits antireflective coating and the third layer 225 has the fourth layer230 as its antireflective coating. The split layer geometry can berecognized by those of ordinary skill in the art of the presentinvention as being an optical trap.

An exemplary preferred embodiment of the present invention includes afirst high refractive index layer with a thickness of approximately 20nm of TiN, a first low refractive index layer with a thickness ofapproximately 50 nm of SiO₂, a second high refractive index layer with athickness of approximately 20 nm of TiN, and a second low refractiveindex layer formed from two layers of low refractive index material, afirst layer with a thickness of approximately 50 nm of SiON and a secondlayer with a thickness of approximately 900 to 1100 nm of SiO₂. A secondexemplary preferred embodiment of the present invention includes a firsthigh refractive index layer with a thickness of approximately 50 nm ofTiN, a first low refractive index layer with a thickness ofapproximately 800 to 1100 nm of SiO₂, a second high refractive indexlayer with a thickness of approximately 75 nm of TiN, and a second lowrefractive index layer with a thickness of approximately 67 nm of SiON.

According to a preferred embodiment of the present invention, adifference in the refractive index of the material used in the highrefractive index layer and the refractive index of the material used inthe low refractive index layer for light in the visible spectrum shouldbe at least 0.25. Furthermore, the material used in the high refractiveindex layer can be a semiconducting metal, a metal oxide, or a metalnitride with a refractive index of at least 1.7 for light in the visiblespectrum. Additionally, the material used in the low refractive indexlayer can be made from one or more insulating metal oxides or metalhalides with a refractive index of at most 1.7 for light in the visiblespectrum.

With reference now to FIGS. 3 a and 3 b, there are shown diagramsillustrating alternate layer arrangements for the antireflectivecoating, according to a preferred embodiment of the present invention.Each of the two low refractive index layers (the second layer 220 andthe fourth layer 230 of FIG. 2 a) of the antireflective layer cancomprise multiple layers of low refractive index materials, such ascombinations of layers of SiO₂ and SiON. The diagram shown in FIG. 3 aillustrates an antireflective coating on an aluminum layer 305comprising two TiN layers 315 and 325 (high refractive index layers)alternating with two combination low refractive index layers 320 and 330made up of two or more layers of SiO₂ and SiON. According to a preferredembodiment of the present invention, the combination low refractiveindex layers 320 and 330 can have similar thickness ranges (5 nm to10000 nm with a preferred thickness range of 10 nm to 2500 nm) as thesingle material low refractive index layers 220 and 230 (FIGS. 2 a and 2b), with the number of alternating layers and their respectivethicknesses being based upon factors such as desired color point,reflectivity, and so forth. In addition to SiO₂ and SiON, other lowrefractive index materials can be used.

With reference now to FIG. 3 b, in addition to the embodiment discussedabove, wherein the two low refractive layers 320 and 330 are made fromalternating layers of low refractive index materials, it is also apreferred embodiment that a first low refractive index layer, such as afirst low refractive index layer 340 of two low refractive index layersbe made from alternating layers of low refractive index materials, whilea second low refractive index layer, such as second low refractive indexlayer 335, be made from a single low refractive index material or viceversa. As shown in FIG. 3 b, the first low refractive index layer 340 isformed with two layers made from two low refractive index materials, afirst layer 345 made from SiON and a second layer 350 made from SiO₂.Although shown as being formed with two alternating layers of lowrefractive index material, more than two alternating layers can be used.Furthermore, it is possible to form the low refractive index layer 335from multiple layers of low refractive index material and the lowrefractive index layer 340 from a single low refractive index material.

With reference now to FIGS. 4 a through 4 c, there are shown diagramsillustrating sequences of events in the manufacture of an integratedcircuit, such as a light modulator array, with an antireflective coatingfor structures in a substrate of the integrated circuit, according to apreferred embodiment of the present invention. A sequence of events 400in the manufacture of an integrated circuit, such as one containing alight modulator array, is shown in FIG. 4 a. The diagram shown in FIG. 4a illustrates the sequence of events 400 in the manufacture of a typicalintegrated circuit and a sequence of events in the manufacture of anactual integrated circuit can vary for different integrated circuits.

Initially, the fabrication of the integrated circuit can begin with theformation of structures in a substrate of the integrated circuit (block402). The structures formed in the substrate can include transistors,conductors, metal layers, vias, and so forth. Once the structures in thesubstrate of the integrated circuit have been formed, an antireflectivecoating can be formed (block 404). The antireflective coating can eitherbe formed on the structures individually or it can be formed on a topsurface of the substrate as a whole and cover all structures in thesubstrate as well as any portion of the substrate not containing astructure. After the antireflective coating has been formed on thesubstrate, a passivation coating can be applied (block 406). Thepassivation coating can be used to protect the substrate, the structureson and in the substrate, the antireflective coating, and so forth.Depending upon the antireflective coating, the passivation coating maynot be needed. For example, if a top layer of the antireflective coatingis formed from SiO₂ and has adequate thickness, then the passivationcoating may not be required, since the passivation coating is typicallymade from SiO₂.

After the application of the passivation coating or the formation of theantireflective layer (if the passivation coating is not needed),external structures for the integrated circuit can be formed (block408). For example, if the integrated circuit is a light modulator arraymaking use of positional micromirrors, then support structures for thepositional micromirrors, as well as the positional micromirrors, can beformed. Following the formation of external structures, any additionaloperations needed to complete the integrated circuit can be completed(block 410). The additional operations can include bonding wire padstogether, forming electrodes, and so on. The integrated circuit is nowcomplete and can undergo singulation, testing, labeling, packaging, andso forth.

The diagram shown in FIG. 4 b illustrates a detailed sequence of events420 in the formation of the antireflective coating on the substrate ofthe integrated circuit. The sequence of events 420 can be illustrativeof the formation of an antireflective coating (block 404, FIG. 4 a). Theformation of the antireflective coating can begin with the formation ofa first high refractive index layer (block 422). According to apreferred embodiment of the present invention, TiN can be used to createthe first high refractive index layer. The first high refractive indexlayer can have a thickness, H1, as specified and illustrated previously.After forming the first high refractive index layer (block 422), a firstlow refractive index layer can be formed (block 424). The first lowrefractive index layer can serve as an antireflective coating for thefirst high refractive index layer. Preferred materials for use in theformation of the first low refractive index layer can be SiO₂ and SiON.However, materials with a refractive index ranging from that of air tothat of TiN can be used. The first low refractive index layer can have athickness, L1, wherein the thickness can range from 5 nm to 10,000 nm,with preferred thicknesses ranging from 10 nm to 2,500 nm.

A second high refractive index layer can now be formed on top of thefirst low refractive index layer (block 426). Again, TiN can be apreferred material for the creation of the second high refractive indexlayer. The second high refractive index layer can have a thickness, H2,in an application where the antireflective coating has four layers.Finally, a second low refractive index layer can be formed (block 428).Preferred materials for use in the formation of the first low refractiveindex layer can be SiO₂ and SiON. However, materials with a refractiveindex ranging from that of air to that of TiN can be used. The first lowrefractive index layer can have a thickness, L1, wherein the thicknesscan range from 5 nm to 10,000 nm, with preferred thicknesses rangingfrom 10 nm to 2,500 nm.

If the antireflective coating is to have more than four layers, theformation of the high refractive index layers and the low refractiveindex layers can continue, with a final layer of the antireflectivecoating being a low refractive index layer.

The diagram shown in FIG. 4 c illustrates a detailed sequence of events440 in the formation of a combination low refractive index layer of theantireflective coating. Each of the low refractive index layers in theantireflective coating (the first low refractive index layer and thesecond low refractive index layer, for example) can be formed frommultiple layers of low refractive index materials. For example, thefirst low refractive index layer can be formed from alternating layersof SiO₂ and SiON. To form a multilayer low refractive index layer, afirst layer can be formed with a thickness, CL1 (block 442), and then asecond layer can be formed with a thickness, CL2 (block 444). Anyadditional layers can also be added to the low refractive index layeruntil a desired number of layers is achieved (block 446). Although thediscussion illustrates the formation of the low refractive index layerfrom alternating layers of two low refractive index materials, more thantwo low refractive index layers can be used. The thicknesses of thealternating layers of low refractive index materials can be dependantupon factors such as desired color point, desired reflectivity, and soforth.

With reference now to FIGS. 5 a and 5 b, there are diagrams illustratingreflectance vs. light wavelength for exemplary light modulator arrayswith and without the antireflective coating, according to a preferredembodiment of the present invention. FIG. 5 a illustrates reflectance(in percentage) vs. light wavelength for a light modulator array withoutthe antireflective coating. As shown in FIG. 5 a, the reflectance canrange from a low of about 20% to a high of about 45% for visible lightspectrum (from 400 nm to 750 nm). FIG. 5 b illustrates reflectance (inpercentage) vs. light wavelength for a light modulator array with theantireflective coating. As shown in FIG. 5 b, the reflectance rangesfrom a low of about 10% to a high of 22% for the visible light spectrum.The antireflective coating significantly reduces the reflectance of thelight modulator array.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the process, machine,manufacture, composition of matter, means, methods and steps describedin the specification. As one of ordinary skill in the art will readilyappreciate from the disclosure of the present invention, processes,machines, manufacture, compositions of matter, means, methods, or steps,presently existing or later to be developed, that perform substantiallythe same function or achieve substantially the same result as thecorresponding embodiments described herein may be utilized according tothe present invention. Accordingly, the appended claims are intended toinclude within their scope such processes, machines, manufacture,compositions of matter, means, methods, or steps.

What is claimed is:
 1. A method for forming an antireflective coating ona semiconductor device, the method comprising: forming a first highrefractive index layer on a reflective surface; forming a first lowrefractive index layer on the first high refractive index layer; forminga second high refractive index layer on the first low refractive indexlayer; and forming a second low refractive index layer on the secondhigh refractive index layer; wherein the forming of at least one of thelow refractive index layers comprises forming a first combination layerfrom a first low refractive index material; and forming a secondcombination layer from a second low refractive index material; whereinthe first combination layer has a first thickness and the secondcombination layer has a second thickness; and wherein the firstthickness and the second thickness are dependent upon a desired colorpoint or desired reflectivity.
 2. A method for forming an antireflectivecoating on a semiconductor device, the method comprising: forming afirst high refractive index layer on a reflective surface; forming afirst low refractive index layer on the first high refractive indexlayer; forming a second high refractive index layer on the first lowrefractive index layer; and forming a second low refractive index layeron the second high refractive index layer; wherein the first highrefractive index layer and the second high refractive index layer areformed from a titanium nitride (TiN) film of compositionTi_(x)N_(y)O_(z) with x, y, and z being integer values and y>x>z; andwherein the first low refractive index layer and the second lowrefractive index layer are formed from materials selected from a groupconsisting of: silicon dioxide (SiO₂) and silicon oxynitride (SiON). 3.The method of claim 2, further comprising forming, on the second lowrefractive index layer, alternate layers of a high refractive indexlayer and a low refractive index layer until a desired number of layersis reached.
 4. The method of claim 2, wherein the forming of at leastone of the low refractive index layers comprises: forming a firstcombination layer from a first low refractive index material; andforming a second combination layer from a second low refractive indexmaterial.